1. Field of the Invention
The present invention relates to a liquid ejection head and an image forming apparatus including a liquid ejection head, and more particularly, to a structure and electrical wiring for a liquid ejection head, and to a method of manufacturing a liquid ejection head.
2. Description of the Related Art
As an image forming apparatus in the related art, an inkjet printer (inkjet recording apparatus) is known, which includes an inlet printer head (liquid ejection head, which is also referred to as, simply, “head”) having an arrangement of a plurality of liquid ejection nozzles and which records an image on a recording medium by ejecting ink (liquid) from the nozzles toward the recording medium while causing the relative movement between the inkjet head and the recording medium.
An inkjet head of an inkjet printer of this kind has pressure generating units. Each pressure generating unit includes, for example, a pressure chamber to which ink is supplied from an ink tank via an ink supply channel, a piezoelectric element which is driven by an electrical signal in accordance with image data, a diaphragm which constitutes a portion of the pressure chamber and deforms in accordance with the driving of the piezoelectric element, and a nozzle which is connected to the pressure chamber. The ink inside the pressure chamber is ejected from the nozzle in the form of a droplet due to the volume of the pressure chamber being reduced by the deformation of the diaphragm. In an inkjet printer, an image is formed on the recording medium by combining dots formed by ink ejected from the nozzles of the pressure generating units.
Ink ejection is controlled by transmitting electrical signals to the piezoelectric elements that are to be driven. Various methods have been proposed with respect to how to arrange the electrical wires for transmitting the electrical signals and how to arrange the substrate having drive ICs (integral circuits), from viewpoints of component counts, manufacturing costs, and compactification of the apparatus.
For example, Japanese Patent Application Publication No. 2003-182076 discloses that ICs (integral circuits) serving as drive circuits are fixed on a bonding substrate which covers the piezoelectric elements, and the ICs are connected with electrodes and connected with each other, by wire bonding. Thereby, the installation surface area can be reduced and a head can be made more compact.
Moreover, Japanese Patent Application Publication No. 2005-254616 discloses that a portion of walls of a common liquid chamber is constituted by a flexible substrate, or the like, thereby reducing the overall size of the head of an inkjet printer.
However, in the invention described in Japanese Patent Application Publication No. 2003-182076 mentioned above, since a connection between ICs and a connection between an IC and an electrode are made by wire bonding, then, in a device such as a printer including a drive unit, there is a possibility of disconnection due to vibrations or impacts, and accordingly reliability is poor. Moreover, since the electrodes to which ICs are connected by wire bonding are provided at the bottom face of a recess shape, then problems arise as to workability and work efficiency in wire bonding. Furthermore, since a common liquid chamber is provided beside a pressure chamber row, then it is necessary to arrange nozzles and a common liquid chamber alternately in order to achieve a matrix configuration of nozzles. There is a possibility that the head increases in size.
In the invention described in Japanese Patent Application Publication No. 2005-254616, similarly to the invention of Japanese Patent Application Publication No. 2003-182076, the electrodes to be connected by wire bonding are provided at the bottom surface of a recess shape, and therefore, reliability is poor and problems of work efficiency may arise. Moreover, a flexible substrate with high-density wirings which is used for the electrical wiring substrate is extracted outside. Hence, the installation space of the head is increased.